“Nature abhors a vacuum.” Variations of this idea, popularized by Aristotle, are a staple of U.S. political rhetoric, generally marshalled by those who argue that the United States should continue some foreign mission — usually a war or military occupation — lest power there pass to an adversary and decrease U.S. security. We are told, for example, that taking troops out of Syria will benefit Russia or Iran; pulling small contingents of forces from West Africa will strengthen China at U.S. expense; exiting Afghanistan will benefit Russia or China.
Pundits also use vacuum fears more generally to warn against surrendering influence in the developing world. Chinese investment in Africa or in Asia via the Belt and Road Initiative is said to exploit a vacuum that the United States should compete to fill. A potential U.S. military exit from the Middle East is said to risk leaving a vacuum that would be a “gift to Putin.”
This idea that power vacuums occur is not entirely wrong. The removal of U.S. forces or spending from a region can indeed create a vacuum, in which other actors gain some influence. The truly bad idea is the claim that vacuums meaningfully benefit U.S. rivals and endanger Americans.
Vacuum theory is essentially an old imperial idea in new, dubious security logic. It says U.S. forces have to run the world so other powers do not and somehow threaten us. Taken to its logical conclusion, that would mean never ending any deployment or war while expanding aid and military presence everywhere. That is, to put it mildly, an expensive proposition.
The theory fails for three reasons. First, those who stand to gain power following U.S. withdrawals tend to be local actors, not great power rivals. Second, the places where vacuums are feared tend to be poor regions with little strategic security value to either the United States or its rivals. Third, U.S. relations with its rivals are not so zero-sum that the gains they do reap from influence in developing countries are worrisome. U.S. security does not depend on predominance everywhere.
Before proceeding to the flaws of the vacuum theory, two caveats are useful. One is that the argument here largely does not address whether U.S. troop deployments create much power or influence at all — a necessary prerequisite to losing it to a vacuum. There is reason to doubt that the presence of U.S. troops in modern war zones generates lasting influence, especially when the deployments are small, as in Syria or Somalia today. Exploring that point properly demands a much longer article. A second caveat is that vacuum arguments, like domino theory or credibility worries, often seem like post hoc rationalizations of a military presence favored for other reasons. But analysts have a responsibility to take even an idea often made in bad faith seriously, if it’s widely made and believed.
The first major reason not to fear vacuums is that actors who gain power tend to be local. Political power vacuums, properly understood, are not an absence of coercive authority; they are the dispersal of it. Pulling out troops can indeed have chaotic results, but generally local governments, militias, and insurgents — not foreign powers — are the ones gathering authority. Past U.S. withdrawals from wars and military occupations, even during the Cold War, show this. U.S. forces left Vietnam, various Latin American countries, and the Philippines without great power rivals rushing into the breach. Those lessons hold today. The difficulties that U.S. forces face in imposing their will in Afghanistan or Iraq would likely be faced by other great powers intervening to try to call the shots.
The second problem with vacuum theory is that it is mostly used to oppose the withdrawal of U.S. troops from poor countries largely useless for building or contesting geopolitical power. Conquest or military occupation pays security dividends when it helps the occupier expand wealth and military capability. Historically, that meant heavily-industrialized countries, energy producers, or areas of geographic vulnerability to the occupier. Due to difficulties nationalism creates in pacifying countries and the increased complexity of extracting their wealth, forcibly occupying even advanced countries is less likely to offer a benefit today.
Regardless, the U.S. occupations whose end we now debate are in states that offer little to reward to occupying states. Syria and Afghanistan are less gifts to other would-be occupiers than civil war management opportunities. Even in states with large oil reserves like Iraq, foreign powers will struggle to take over the profits of production and would likely energize heavier opposition by trying. Such occupations tend to drain resources rather than providing cumulative gains that enhance power.
The third and final flaw in the vacuum theory follows from the limits of great power competition. U.S. entry into World War II and the Cold War was fueled in part by fears that the unification of much of Eurasia — with its vast resources and industrial might — would directly threaten the United States, either through military attack or closure of trade.
Today, geography, wealth, and military power, especially in the form of nuclear weapons, make U.S. security profound. No would-be hegemon much threatens the political independence of Western European states and East Asian allies like Japan and South Korea. More to the point, the gains that China or Russia might make in the Middle East or developing world would do little to alter the balance of power. China handing out loans in South Asia or its firms buying mines or energy contracts in Africa has little effect on U.S. security.
The truth is that the vacuum theory is basically backwards. Leaving vacuums for rivals to fill in the countries where U.S. forces have recently fought wars is less a gift to them than an invitation to folly. It is more sensible to want enemies to suffer the bloody troubles the United States did trying to manage so much of the world than to expensively prevent them from trying.
CSIS does not take specific policy positions; accordingly, all views expressed above should be understood to be solely those of the author.
(Photo Credit: U.S. Air Force photo by Chief Master Sgt. Richard Simonsen, Nuristan Provincial Reconstruction Team Public Affairs)